The evolution of wireless systems has followed two different paths: radio and television broadcasting. Wireless communication started with paging and dispatch systems. Wireless voice communication became a booming industry in the past two decades. The last five years has witnessed many wireless data communication systems such as wireless local area network (WLAN) and broadband wireless access (BWA) systems. With digitalization and the advancements of the digital communication technology, digital broadcasting has become a new trend with digital video broadcast (DVB) and digital audio broadcast (DAB) systems as examples.
Recently, there is a trend of merging wireless technologies to provide support to multimedia applications in integrated environments. The third generation (3G) wireless communication systems have already integrated voice and data services. The recent WiMax technology is focused on a single platform to support broadband application with quality of service (QoS).
Naturally, the integration of the broadcast and the communication systems is the next step in the evolution of the wireless systems, but involves many challenges. For example, the broadcast system needs to deal with broadcast channels that have different characteristics. Also, the scheduler needs to optimally work with two downlink transmission paths: the broadcast channel and the regular (individual) channel. However, integration of a broadcast system with a communication system without sharing certain control information is not an optimized solution.
In a broadcasting system, content data from the source is delivered to multiple transmission base stations, which broadcast to receivers using a particular transmission method such as Orthogonal Frequency Division Modulation (OFDM). To alleviate the problem of interference from different base stations, the broadcasting data is simultaneously transmitted by all the base stations using same time/frequency resource. This type of network configuration is commonly known as the single frequency network (SFN), which has been used in applications such as the digital video broadcasting (DVB) system.
In the case of the DVB, the broadcasting video data, which is in the format of Moving Picture Experts Group 2 (MPEG-2) transport streams, is coded into a mega-frame format and is distributed to the base stations with a time stamp in the synchronized bit stream. The base stations are all synchronized to a common time source and use the time stamp to synchronize exact transmission time of the broadcast data. However, recently more and more new wireless data network infrastructures use packet data networks as their backbone. A packet data network has a bursty packet arrival pattern, random receiving packet order and multiple distribution paths, which is significantly different from those of the MPEG-2 transport streams. Therefore, the DVB approach is not suitable for a packet data network and for a SFN video broadcasting that uses a packet data network backbone.